The Santa Cruz River is about 600 ft in the Sunset Road reach. The channel slope is 0.3%, and Manning's roughness coefficient is 0.06. The design flow discharge is 70,000 cfs. For the proposed sunset bridge, the maximum pier spacing is 150 ft, and the minimum pier diameter is 6 ft. The drag coefficient is 2.0. If the cross section is approximately rectangular, and the approaching flow to the bridge is shallow ( R y ) and steady uniform. Calculate the depth of approaching flow, and the minimum backwater caused by the bridge